Dry season cues root disease alert

SESSION: Attending a root disease risk management course for agronomists at the Waite research precinct in Adelaide were Clare Svilans, Western AG, Kaniva (Victoria), and Luke Harrop, from Kadina (SA). Photo: GRDC

SESSION: Attending a root disease risk management course for agronomists at the Waite research precinct in Adelaide were Clare Svilans, Western AG, Kaniva (Victoria), and Luke Harrop, from Kadina (SA). Photo: GRDC

Grain growers in the southern cropping region who have experienced a dry growing season this year are being warned of a potential increase in the risk of some soilborne diseases in 2019.

Rhizoctonia root rot and crown rot are two cereal diseases likely to pose a problem in parts of South Australia and Victoria where rainfall was below average this year.

A lack of rainfall has reduced the breakdown of cereal stubbles in pulse and oilseed break crops, promoting the risk of disease next season.

Soilborne disease experts, supported by the Grains Research and Development Corporation, are advising growers to know their paddocks’ disease risk profile well ahead of sowing by having their soils tested.

Leader of the South Australian Research and Development Institute’s (SARDI) soil biology and molecular diagnostics group Alan McKay said the risk of disease in 2019 would be heightened where growers decided to sow wheat back into this year’s failed wheat crops.

“I expect rhizoctonia and crown rot will be the main issues as a result of low growing season rainfall, and growers should also keep an eye on cereal cyst nematode as levels have been trending higher over the past five years,” he said.

“Rhizoctonia, especially, has a competitive advantage in low moisture situations and its levels have almost certainly increased this year,” Mr McKay added.

Mr McKay said should there be a dry summer and if the break to the season was late, crop seedlings would be exposed to high levels of rhizoctonia next year.

Rhizoctonia root rot can reduce cereal yields by more than 50 percent, with barley the most susceptible.

Testing for crown rot ahead of sowing in 2019 is also being strongly encouraged.

SARDI research scientist Marg Evans said while crown rot required moisture in autumn to infect the crop, a dry spring such as the one experienced this year would favour expression of the disease.

“The fungus grows quicker in water-stressed plants and in warm weather, and damage is more likely in intensive cereal rotations, especially in durum,” Ms Evans said.

Whiteheads can be symptomatic of crown rot, but given these only appear in seasons with a dry finish the absence of whiteheads does not indicate freedom from crown rot which survives for up to four years in plant residues or stubbles.

Dr McKay said Australian grain growers incur, on average, more than $200 million each year in lost production because of cereal root diseases.